U.S. patent number 4,648,345 [Application Number 06/774,565] was granted by the patent office on 1987-03-10 for propeller system with electronically controlled cyclic and collective blade pitch.
This patent grant is currently assigned to Ametek, Inc.. Invention is credited to Frederick R. Haselton, Lawrence A. Mackey, John L. Wham.
United States Patent |
4,648,345 |
Wham , et al. |
March 10, 1987 |
Propeller system with electronically controlled cyclic and
collective blade pitch
Abstract
A plurality of blades extend radially from a hub which is
rotated by a motor about a drive axis. Each blade has a root which
is rotatably connected to the hub so that it can be independently
twisted to vary the pitch thereof relative to the drive axis. A
plurality of electromagnets are annularly positioned adjacent the
hub so that permanent magnets connected to the roots of
corresponding blades can be attracted and/or repelled to induce
twisting motion in the blades as the hub rotates about its drive
axis. A control circuit receives input commands for a manual
control device and causes predetermined electrical signals to be
applied to the electromagnets for simultaneously varying the pitch
of the blades. The pitch of the blades can be varied cyclically and
collectively in accordance with any real continuous function, and
not just sinusoidally as in the case of prior mechanical linkages
employing swash plates. A vessel equipped with the propeller system
at the fore and aft ends thereof can be precisely maneuvered in six
degrees of freedom.
Inventors: |
Wham; John L. (San Diego,
CA), Mackey; Lawrence A. (Santee, CA), Haselton;
Frederick R. (Cookeville, TN) |
Assignee: |
Ametek, Inc. (El Cajon,
CA)
|
Family
ID: |
25101635 |
Appl.
No.: |
06/774,565 |
Filed: |
September 10, 1985 |
Current U.S.
Class: |
114/338; 416/98;
416/158; 416/3; 416/155; 440/50 |
Current CPC
Class: |
B63H
3/06 (20130101); B63G 8/16 (20130101); B63H
3/002 (20130101) |
Current International
Class: |
B63G
8/00 (20060101); B63H 3/00 (20060101); B63H
3/06 (20060101); B63G 8/16 (20060101); B63G
008/16 () |
Field of
Search: |
;114/338,330,126
;440/49,50,93 ;416/155,3,98 ;244/17.25 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
William G. Wilson, "Effects of Configurational Changes on Tandem
Propeller Performance," Cornell Aeronautical Laboratory Report No.
AG-1634-V-9, Feb. 1966. .
Roy S. Rice, Jr., "Experimental Studies of Tandem Propeller
Performance at Static Conditions," Cornell Aeronautical Laboratory
Report No. AG-2381-K-2, Feb. 1968. .
F. R. Haselton, "Tandem Propeller Tailoring Technique," Naval
Engineers Journal, Aug. 1965, pp. 621-624. .
J. Cantwell & S. Cap "Computer Mission Simulation for
Parametric Design of Undersea Vehicles," IEEE Ocean '75, pp.
860-869. .
F. R. Haselton "Tandem Propeller in Review," J. Hydronautics, vol.
3, No. 4, Oct. 1969, pp. 161, 163, 165, 167. .
Richard S. Brannin, "Tandem Propellers", pp. 37-44..
|
Primary Examiner: Basinger; Sherman D.
Assistant Examiner: Salmon; Paul E.
Attorney, Agent or Firm: Baker, Maxham & Jester
Claims
We claim:
1. A propeller system, comprising:
a plurality of blades;
hub means for supporting the blades for rotation about a common
drive axis and so that each blade can be independently twisted
about a corresponding blade axis to vary the pitch of the blade
relative to the drive axis; and
means for rotating the hub means about the drive axis and for
twisting the blades to non-sinusoidally vary a cyclic pitch and a
collective pitch of the blades during rotation of the hub means,
including a plurality of permanent magnets, each rigidly connected
to a root of a corresponding blade.
2. A propeller system according to claim 1 wherein the hub rotating
and pitch varying means further includes a plurality of
electromagnets for inducing motion of the permanent magnets to
thereby twist the blades when electrical signals are applied to the
electromagnets.
3. A propeller system according to claim 2 wherein the hub rotating
and pitch varying means further includes control means for
generating the electrical signals in response to a set of commands
inputted thereto.
4. A propeller system according to claim 3 wherein the control
means includes at least one manual control device for generating
analog electrical signals representative of the set of commands
inputted by manual actuation of the control device, a digital
processor, a memory connected to the processor for storing a
control program, an analog-to-digital converter operatively
connecting the manual control device and the processor, a plurality
of amplifiers each operatively connected to a corresponding one of
the electromagnets for energizing the same, a sensor for inputting
an electrical signal to the processor representative of an angular
position of the hub means relative to the drive axis, and a
digital-to-analog converter operatively connecting the processor
and the amplifiers for allowing the processor to cause
predetermined electrical signals to be applied to the amplifiers in
accordance with the inputted commands, the angular position signal
and the control program.
5. A propeller system according to claim 2 wherein the rotation of
the hub means is accomplished by coordinated energization of the
electromagnets.
6. A propeller system according to claim 2 wherein each
electromagnet has a generally U-shaped configuration and the
plurality of electromagnets define a radially outwardly opening
channel in which the permanent magnets rotate.
7. A propeller system according to claim 1 wherein the hub rotating
and pitch varying means further includes motor means for rotating
the hub means about the drive axis.
8. A propeller system according to claim 1 wherein each blade is
configured so that a center of fluid pressure generated on each
blade substantially coincides with the corresponding blade axis of
the blade.
9. A propeller system according to claim 1 wherein the blades
extend at an acute angle relative to the drive axis.
10. A propeller system, comprising:
a plurality of blades;
hub means for supporting the blades for rotation about a common
drive axis and so that each blade can be indpendently twisted about
a corresponding blade axis to vary the pitch of the blade relative
to the drive axis; and
means for rotating the hub means about the drive axis and for
twisting the blades to vary a cyclic pitch and a collective pitch
of the blades during rotation of the hub means, including a
plurality of permanent magnets, each rigidly connected to a root of
a corresponding blade.
11. A propeller system according to claim 10 wherein the hub
rotating and pitch varying means further includes a plurality of
electromagnets for inducing motion of the permanant magnets to
thereby twist the blades when electrical signals are applied to the
electromagnets.
12. A propeller system according to claim 11 wherein the hub
rotating and pitch varying means further includes control means for
generating the electrical signals in response to a set of commands
inputted thereto.
13. A propeller system according to claim 12 wherein the control
means includes at least one manual control device for generating
analog electrical signals representative of the set of commands
inputted by manual actuation of the control device, a digital
processor, a memory connected to the processor for storing a
control program, an analog-to-digital converter operatively
connecting the manual control device and the processor, a plurality
of amplifiers each operatively connected to a corresponding one of
the electromagnets for energizing the same, a sensor for inputting
an electrical signal to the processor representative of an angular
position of the hub means relative to the drive axis, and a
digital-to-analog converter operatively connecting the processor
and the amplifiers for allowing the processor to cause
predetermined electrical signals to be applied to the amplifiers in
accordance with the inputted commands, the angular position signal
and the control program.
14. A propeller system according to claim 11 wherein the rotation
of the hub means is accomplished by coordinated energization of the
electromagnets.
15. A propeller system according to claim 11 wherein each
electromagnet has a generally U-shaped configuration and the
plurality of electromagnets define a radially outwardly opening
channel in which the permanent magnets rotate.
16. A propeller system according to claim 10 wherein the hub
rotating and pitch varying means further includes motor means for
rotating the hub means about the drive axis.
17. A propeller system according to claim 10 wherein each blade is
configured so that a center of fluid pressure generated on each
blade substantially coincides with the corresponding blade axis of
the blade.
18. A propeller system according to claim 10 wherein the blades
extend at an acute angle relative to the drive axis.
19. A submersible vessel, comprising:
an elongate hull;
a first propeller mounted adjacent a fore end of the hull for
rotation about a longitudinal axis of the hull;
a second propeller mounted adjacent an aft end of the hull for
rotation about the longitudinal axis of the hull;
each of the propellers including a plurality of blades and hub
means for supporting the blades for rotation about a common drive
axis and so that each blade can be independently twisted about a
corresponding blade axis to vary the pitch of the blade relative to
the drive axis; and
means for rotating the hub means of the first and second propellers
about the longitudinal axis and for varying a cyclic pitch and a
collective pitch of the blades during rotation of the hub means for
maneuvering the hull in six different degrees of freedom, including
a plurality of permanent magnets, each rigidly connected to a root
of a corresponding blade.
20. A submersible vessel according to claim 19 wherein the hub
rotating and pitch varying means further includes a plurality of
electromagnets for inducing motion of the permanent magnets to
thereby twist the blades when electrical signals are applied to the
electromagnets.
21. A submersible vessel according to claim 20 wherein the hub
rotating and pitch varying means further includes control means for
generating the electrical signals in response to a set of commands
inputted thereto.
22. A submersible vessel according to claim 21 wherein the control
means includes at least one manual control device for generating
analog electrical signals representative of the set of commands
inputted by manual actuation of the control device, a digital
processor, a memory connected to the processor for storing a
control program, an analog-to-digital converter operatively
connecting the manual control device and the processor, a plurality
of amplifiers each operatively connected to a corresponding one of
the electromagnets for energizing the same, a sensor for inputting
an electrical signal to the processor representative of an angular
position of the hub means relative to the drive axis, and a
digital-to-analog converter operatively connecting the processor
and the amplifiers for allowing the processor to cause
predetermined electrical signals to be applied to the amplifiers in
accordance with the inputted commands, the angular position signal
and the control program.
23. A submersible vessel according to claim 20 wherein the rotation
of the hub means is accomplished by coordinated energization of the
electromagnets.
24. A submersible vessel according to claim 20 wherein each
electromagnet has a generally U-shaped configuration and the
plurality of electromagnets define a radially outwardly opening
channel in which the permanent magnets rotate.
25. A submersible vessel according to claim 19 wherein tne hub
rotating and pitch varying means further includes motor means for
rotating the hub means about the longitudinal axis.
26. A submersible vessel according to claim 19 wherein each blade
is configured so that a center of fluid pressure generated on each
blade substantially coincides with the corresponding blade axis of
the blade.
27. A submersible vessel according to claim 19 the blades extend at
an acute angle relative to the drive axis.
28. A propeller system, comprising:
a plurality of blades each having a root;
means for supporting the blades for rotation about a common drive
axis and so that each blade can be independently twisted about a
corresponding blade axis to vary the pitch thereof relative to the
drive axis;
means for rotating the blade supporting means about the drive axis;
and
means for twisting the blades during rotation of the blade
supporting means to independently vary a cyclic pitch of the blades
and a collective pitch of the blades during rotation of the blade
supporting means about the drive axis, including a plurality of
electromagnets annularly spaced about the drive axis radially
inward of roots of the blades, each electromagnet being capable of
being energized to attract or repel a member rigidly connected to a
root of a selected blade to generate a torque on the selected blade
about its blade axis as the selected blade moves past the energized
electromagnet.
29. A propeller system, comprising:
a plurality of blades each having a root;
means for supporting the blades for rotation about a common drive
axis and so that each blade can be independently twisted about a
corresponding blade axis to vary the pitch thereof relative to the
drive axis;
means for rotating the blade supporting means about the drive axis;
and
means for twisting the blades during rotation of the blade
supporting means to independently vary a cyclic pitch of the blades
and a collective pitch of the blades during rotation of the blade
supporting means about the drive axis, including a plurality of
electromagnetic means spaced annularly about the drive axis
adjacent the roots of the blades for each generating a
predetermined torque on a selected blade as it moves thereby.
30. A propeller system according to claim 29 and further comprising
at least one manual control device for generating analog electrical
signals representative of a set of commands inputted by manual
actuation of the control device, a digital processor, a memory
connected to the processor for storing a control program, an
analog-to-digital converter operatively connecting the manual
control device and the processor, a plurality of amplifiers each
operatively connected to a corresponding one of the electromagnetic
means, a sensor for inputting an electrical signal to the processor
representative of an annular position of the blade supporting means
relative to the drive axis, and a digital-to-analog converter
operatively connecting the processor and the amplifiers for
allowing the processor to cause predetermined electrical signals to
be applied to the amplifiers in accordance with the inputted
commands, the angular position signal and the control program.
31. A propeller system, comprising:
a plurality of blades;
a generally cylindrical hub;
means for supporting the hub for rotation about a drive axis;
a plurality of shafts, each having an outer end rigidly connected
to a root of a corresponding blade to define a blade axis, the
shafts extending radially through the hub at circumferentially
spaced locations around the hub and being rotatable to twist the
blades about their blade axis;
a plurality of permanent magnets, each rigidly attached to an inner
end of a corresponding shaft;
a plurality of electromagnets; and
means for supporting the electromagnets in annularly spaced
relationship about the drive axis radially inward of the permanent
magnets, each electromagnet being capable of being energized to
induce motion of an adjacent permanent magnet to thereby twist the
blade connected thereto as the blades rotate about the drive
axis.
32. A propeller system, comprising:
a plurality of blades;
means for supporting the blades for rotation about a common drive
axis and to that each can be independently twisted about a
corresponding blade axis to vary the pitch thereof relative to the
drive axis;
a plurality of electromagnetic means positioned in a plurality of
fixed locations annularly spaced about the drive axis adjacent the
roots of the blades, each being separately energizable to generate
a torque or a selected blade as it moves thereby; and
control means for energizing the electromagnets in a coordinated
manner to cause the blade supported means to rotate about the drive
axis and to independently vary a cyclic pitch of the blades and a
collective pitch of the blades as the blade supporting means
rotates about the drive axis.
Description
BACKGROUND OF THE INVENTION
The present invention relates to impeller type propulsion systems,
and more particularly, to a propeller system adapted for precision
control of a submersible vehicle in six different degrees of
freedom.
There are many uses for an unmanned (remotely piloted) deep
submersible ocean vehicle such as maintenance and repair of
underwater oil well facilities, location and recovery of sunken
aircraft and underwater surveying. Commands and sensor data from
cameras and other on-board instrumentation may be transmitted to
and from the vehicle via a tether or sonar. Such a deep submersible
vehicle must be capable of a high degree of maneuverability and
precision control in a reliable manner in order to effectively
accomplish such tasks. In particular, such a submersible vehicle
must be able to make precise translational and rotational movements
relative to the surge (fore-aft), sway (athwartship), and heave
(vertical) axes. Such a vehicle must also be capable of maintaining
any attitude to perform its tasks, and it must be able to exert
large forces and moments with precision.
Heretofore remotely piloted deep submersible vehicles for
performing this type of work have typically included a frame or
sled with a viewing camera, lights, robot arms and a plurality of
outboard thrusters for movement relative to the three different
axes. These thrusters have typically been hydraulic and have
required complex control mechanisms. The efficiency and response
time of such thrusters and their ability to accomplish precision
maneuvers are limited.
In U.S. Pat. No. 3,101,066 of Haselton there is disclosed a
submarine with fore and aft counter-rotating propellers, and
mechanisms for controlling the cyclical and collective pitch of the
blades of each of the propellers independently for maneuvering the
vehicle in six degrees of freedom. Mechanisms which have heretofore
existed for accomplishing cyclic and collective pitch control have
typically been complex mechanical arrangements similar to the swash
plate mechanisms in helicopters. Such mechanisms require a great
deal of maintenance and are therefore unsuitable for submarine use.
In addition, they can only change blade pitch sinusoidally, i.e.
the blade angle alpha varies as a sinusoidal function of the
angular position theta of the blade relative to the rotational axis
of the propeller, owing to the geometry involved in a swash plate
mechanism. This imposes a limitation on the ability to achieve
precise maneuvers.
SUMMARY OF THE INVENTION
It is the primary object of the present invention to provide an
improved system for varying the pitch angle of the blades of a
propeller during rotation thereof.
It is another object of the present invention to provide an
improved system for varying the pitch angle of a plurality of
blades of a propeller both cyclically and collectively.
It is another object of the present invention to provide a system
for varying the pitch angle of a plurality of blades of a propeller
both cyclically and collectively in a non-sinusoidal manner.
It is another object of the present invention to provide a system
for controlling the cyclic and collective pitch of the blades of a
propeller without any swash plate or other mechanical linkages
between the blades and the control.
It is another object of the present invention to provide an
electronic control system for simultaneously varying the pitch of a
plurality of blades of a propeller both cyclically and
collectively.
It is another object of the present invention to provide an
improved propulsion system for precision maneuvering a submersible
vehicle in six degrees of freedom.
According to the illustrated embodiment of the present invention, a
plurality of blades extend radially from a hub which is rotated by
a motor about a drive axis. Each blade has a root which is
rotatably connected to the hub so that it can be independently
twisted to vary the pitch thereof relative to the drive axis. A
plurality of electromagnets are annularly positioned adjacent the
hub so that permanent magnets connected to the roots of
corresponding blades can be attracted and/or repelled to induce
twisting motion in the blades as the hub rotates about its drive
axis. A control circuit receives input commands for a manual
control device and causes predetermined electrical signals to be
applied to the electromagnets for simultaneously varying the pitch
of the blades. The pitch of the blades can be varied cyclically and
collectively in accordance with any real continuous function, and
not just sinusoidally as in the case of prior mechanical linkages
employing swash plates. A vessel equipped with the propeller system
at the fore and aft ends thereof can be precisely maneuvered in six
degrees of freedom.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a submersible vessel equipped with
the propeller system of the present invention at the fore and aft
ends thereof.
FIG. 2 is an enlarged, fragmentary side elevation view of the
propeller and drive motor at the fore end of the vessel.
FIG. 3 is a further enlarged fragmentary side elevation view
illustrating a portion of the propeller of FIG. 2 with its pitch
variation mechanisms.
FIG. 4 is a diagrammatic illustration of the relationship of the
plurality of electromagnets and the permanent magnet connected to
the root of each blade.
FIG. 5 is a diagrammatic illustration of the manner in which the
position of each of the blades on the propeller is used in cyclic
and collective blade pitch control.
FIG. 6 is a block diagram of the control circuit of the preferred
embodiment of the propeller system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The entire dislosure of U.S. Pat. No. 3,101,066 of Haselton is
incorporated herein by reference.
Referring to FIG. 1 a submersible vessel 10 has a streamlined
elongate hull 12 which is tapered at its fore and aft ends.
Propellers 14 and 16 are mounted adjacent the fore and aft ends of
the hull, respectively, with their rotational drive axes coincident
with the central longitudinal axis of the hull. Each of the
propellers has six radially extending, circumferentially spaced
variable pitch blades 18. The cyclic and collective pitch the
blades on each of the propellers may be independently varied to
precisely maneuver the vessel in six degrees of freedom. These
include translational and rotational movement relative to the
illustrated surge (fore-aft), sway (athwartship), and heave
(vertical) axes. The vessel is thus propelled and steered via the
twin propellers 14 and 16 and no rudders are required.
Referring to FIG. 2, each of the propellers such as 14 is driven
and controlled by similar mechanisms. A hub 20 for supports the
blades 18 for rotation about a common drive axis 22 illustrated in
phantom lines and for permits the blades to be twisted about
corresponding blade axes such as 24 (FIG. 3). The root of each
blade is connected to a corresponding shaft 26 which extends
radially through a hole in the hub and is journaled therein with
suitable bearings (not illustrated) to permit free rotation of the
blade. The peripheral portion of the hub 20 interfaces with the
hull 12 so as to function as a streamlined continuation of the hull
while permitting relative rotation therebetween. As is
conventional, the vessel 10 may have means not illustrated for
permitting water to be pumped in and out of portions of the hull
for buoyancy control. Hub 20 may be provided with various seals and
housings readily apparent to one skilled in the art in order to
prevent sea water from contacting the variable blade pitch
mechanisms hereafter described.
Referring again to FIG. 2, each of the blades 18 is slightly
inclined in the aft direction so that there is an acute angle
between the leading and trailing edges of each blade and its axis
24. There is also an acute angle between each of the blades and the
drive axis 22. An electric, hydraulic or other motor 28 is
drivingly connected to the hub 20 via drive shaft 30. Each blade
preferrably has an airfoil cross-section and is configured so that
the center of fluid pressure P on the blade (FIG. 3) coincides with
the twist axis 24 of the blade. This minimizes the amount of
spindle torque required to twist the blade during submerged
rotation of the propeller 14. Referring to FIGS. 2 and 5, the pitch
of each blade with respect to the drive axis 22 of the propeller is
designated by the angle alpha. The position of the individual
blades about the drive axis 22 as the propeller rotates is
designated by the angle theta.
Referring to FIG. 3, a permanent magnet such as 32 is rigidly
connected to the inner end the shaft 26 of each of the blades 18. A
plurality of stationary electromagnets 34 are positioned inside the
hub 20 for inducing motion of the permanent magnets as the hub
rotates to thereby permit the pitch of the blades to be cyclically
and collectively controlled without any direct mechanical
connection to the blades. Each electromagnet 34 includes a
generally U-shaped metal element 36 defining a pair of
longitudinally spaced poles whose strength and polarization (North
or South) may be controlled by applying predetermined electrical
signals to a coil 38 wound about a segment of the metal element 36.
As illustrated in FIGS. 3 and 4, the U-shaped metal elements 36 of
the plurality of electromagnets are secured at annularly spaced
locations about the peripheral edge of a stationary supporting disk
40 via fasteners 42. As illustrated in FIG. 4, the U-shaped metal
elements 36 are parallel and closely spaced to define a radially
outwardly opening channel 44 in which the permanent magnets travel
during rotation of the hub 20 as illustrated in FIG. 3. Referring
again to FIG. 4, and by way of example, the coil on a given
electromagnet 34' may be energized to generate poles n and s of
predetermined magnetic strength which repel the poles N and S of
the immediately adjacent permanent magnet 32'. Clearly only one of
the poles of the permanent magnet need be attracted or repelled to
twist the blade 18, however by affecting both poles greater spindle
torque can be generated. It is also clear that the four
electromagnets immediately adjacent to the electromagnet 34' in
FIG. 4 can be energized to further increase the spindle torque on
the blade 18 attached to the permanent magnet 32' when that
permanent magnet is in its instantaneous rotational position
illustrated in FIG. 4.
Referring to FIG. 6, a control circuit for simultaneous independent
control of the pitch of the blades 18 is illustrated in block
diagram form. Analog signals representative of maneuvering commands
are generated by manual actuation of a set of control devices 46
such as joy sticks and control knobs. These analog signals are fed
to a microprocessor 48 via analog-to-digital converter 50. A
tachometer or other sensor device 52 proximate the hub 20 or drive
shaft 30 sends digital signals to the microprocessor 48
representative of the angular position of each of the six blades 18
about the drive axis. For example, a certain pulse count may
indicate that blade A (FIG. 5) is at position theta sub 1, blade D
is at position theta sub n and so forth. All six blades, namely
A-F, of the propeller 14 are illustrated diagrammatically in FIG.
5. The coils 38 (FIG. 6) of each of the electromagnets are
connected to corresponding amplifiers 54 which are in turn
connected to the microprocessor 48 via digital-to-analog converter
56. Using a program stored in memory 58 the microprocessor causes
predetermined currents to be applied to the selected ones of the
coils 38 for the appropriated time intervals so that the
electromagnets adjacent the permanent magnets 32 connected to each
of the six propeller blades 18 will be moved the appropriate
amounts to thereby provide the particular cyclic and collective
pitch control required to maneuver the vessel in accordance with
the commands inputted via manual controls 46. The microprocessor
"knows" the angular position theta of each of the blades A-F around
the drive axis 22 at any given instant of time from the output of
the tachometer 52 and therefore "knows" which of the electromagnets
to energize and in what polarities and amounts to produce the
desired different pitches alpha sub A through alpha sub F at any
given instant to achieve the commanded maneuver.
By way of example, the amplifiers 54 may include FET "SMART POWER"
devices. There may be three-hundred and sixty electromagnets 34 to
ensure an adequate precision in pitch control. Five electromagnets
may be energized simultaneously adjacent any given instantaneous
position of a given blade. Thus, where there are a total of
three-hundred electromagnets, only thirty may be energized at any
particular instant. In a typical unmanned submersible vessel the
propeller 14 may rotate at a relatively slow speed of one-hundred
and eighty RPM. Microprocessors are commercially available that
operate at extremely high speeds, such as one megahertz. In the
foregoing example it would take roughly two milliseconds for one of
the permanent magnets to travel the distance between two adjacent
electromagnets. In this time the microprocessor could do roughly
two thousand floating point operations. This is more than enough
computing capability to enable the microprocessor to calculate and
apply the next set of currents that must be applied to next
successive set of thirty electromagnets before the blades have
traveled a circumferential distance equal to that separating
successive blades. The control circuit of FIG. 6 can simultaneously
control the electromagnets of both the fore and aft propellers 14
and 16 to enable rapid response time maneuvering of the vessel 10
in six degrees of freedom. In contrast to prior cyclic and
collective pitch control systems which have employed complex
mechanical linkages employing swash plates, our invention permits
the pitch control to be accomplished in accordance with
non-sinusoidal as well as sinusoidal functions. If cyclic and
collective pitch is limited to sinusoidal control then the vessel
would lose its capability to be independently maneuvered with
respect to the three control axes, i.e. surge, sway and heave. The
blades control function may be defined so as to extend over more
than one revolution of the hub or over a partial revolution. Since
the means for inducing twisting motion in the blades have no direct
mechanical connection to the blades response time is very rapid,
weight and complexity are reduced, and reliability is greatly
increased. With our system it is possible, for example, to achieve
athwartship and vertical thrust which are a large percentage of the
achievable fore-aft thrust. For example, the vessel 10 could
achieve one-thousand pounds of surge thrust and five-hundred pounds
of sway and/or heave thrust. A simple inexpensive electric motor
may rotate the hubs a constant uniform velocity with pitch being
varied for speed and directional control. Because the multiple
outboard thrusters are eliminated the vessel is lighter and more
maneuverable than existing unmanned submersible vessels. For
example, the vessel can attach a single robot arm to a bolt, move
the arm to tighten the bolt while the torque is immediately
countered with a specific propeller thrust.
Details of the cyclic and collective pitch control required to
maneuver in the six degrees of freedom are well known to persons
skilled in the art. See for example "Effects of Configurational
Changes on Tandem Propeller Performance" by William G. Wilson dated
February, 1966 and prepared for the Office of Naval Research
Mathematical Sciences Division, Department of the Navy, CAL Report
No. AG-1634-V-9. See also "Experimental Studies of Tandem Propeller
Performance at Static Conditions" by Roy S. Rice, Jr. dated Feb. 2,
1968 and prepared for the Department of the Navy, Naval Ship
Systems Command, CAL Report No. AG-2381-K-2.
Having described a preferred embodiment of our propeller system, it
should be understood that modifications and adaptations of our
invention will occur to those skilled in the art. For example, the
separate drive motor 28 could be eliminated and the hub rotated by
coordinated energization of the electromagnets. A vernier state
sequencer controller could be used to precisely control the
transitional phase between successive sets of five electromagnets.
Therefore, the protection afforded our invention should only be
limited in accordance with the scope of the following claims.
* * * * *